Supplemental Material

Supplementary Captions

Table S1. COVID-19 movement control order measures (Bernama, 2020a; Bernama 2020b;

Md Shah et al., 2020; Prime Minister’s Office, 2020a; Prime Minister’s Office, 2020b)

Table S2. Average concentration, variations before and during MCOs and relative change (%) of: PM2.5, CO, NO2, and SO2 for sub-urban stations.

Table S3. Average concentration, variations before and during MCOs and relative change (%) of: PM2.5, CO, NO2, and SO2 for urban stations.

Table S4. Average concentration, variations before and during MCOs and relative change (%) of PM2.5, CO, NO2, and SO2 for Industrial stations.

Table S5. Average concentration, variations before and during MCOs and relative change (%) of: PM2.5, CO, NO2, and SO2 for rural stations.

Table S1. COVID-19 movement control order measures (Bernama, 2020a; Bernama 2020b; Md Shah et al., 2020; Prime Minister’s Office, 2020a; Prime Minister’s Office, 2020b)

Date Measures Location January 25, 2020 First case of COVID-19 reported in March 18 – March Movement Control Order Phase 1 Entire country 31, 2020  All mass gathering is prohibited  All business services and educational institution were closed except for essential ones (e.g., water, electricity, energy, telecommunications, postal, transportation, banking, health, pharmacy, airport, safety, defense, cleaning, retail, and food supply)  All citizens have been prohibited from leaving the country  Foreigners/ visitors restricted from entering the country March 27 – April, 14 Enhanced Movement Control Order (EMCO) , 2020  All residents and people who were in the areas Johor are not allowed to leave and no one can enter during the EMCO period.  All business activities had been ordered to close.  Roadblocks have been set-up and all entrance and exit points to the area had also been closed.  Drones were deployed to monitor the movement of the residents in the area. Enhanced Movement Control Order (EMCO) Selangor Mansion and  All residents and people who were in the areas Malayan Mansion are not allowed to leave and no one can enter buildings during the EMCO period.  All business activities had been ordered to close except for shops selling essential items in the buildings  All entrance and exit points to the area had also been closed March 30- April 13, Enhanced Movement Control Order (EMCO) Sungai Lui, Hulu 2020  All residents and people who were in the areas Langat Selangor are not allowed to leave and no one can enter during the EMCO period.  All business activities had been ordered to close  Roadblocks have been set-up and all entrance and exit points to the area had also been closed April 1 – April 14, Movement Control Order Phase 2 Entire Country 2020  Movements were restricted to a 10 kilometre radius from homes only to purchase or deliver food, daily necessities, and medicine.  Businesses premises selling essential items including supermarkets and petrol stations are to operate from 8 am to 8 pm only. April 14 – April 28, Enhanced Movement Control Order (EMCO) Jalan Masjid India, 2020  All residents and people who were in the areas Kuala Lumpur are not allowed to leave and no one can enter during the EMCO period.  All business activities had been ordered to close.  All entrance and exit points to the area had also been closed. April 15 – April 28, Movement Control Order Phase 3 Entire Country 2020  School and universities had been told to implement online learning.  Ministry of International Trade and Industry (MITI) has listed down several sectors that were allowed to operate with restricted conditions.  All citizen was required to stay at home but were still allowed to go out and get essential supplies April 29 – May 3, Movement Control order Phase 4 Entire Country 2020  Movements were still restricted to a 10- kilometre radius from homes only to purchase or deliver food, daily necessities, and medicine.  Students stranded at the university were allowed to go home with proper guidelines (stage by stage and only using buses that is provided by the university management May 4, 2020 – 9 June Conditional Movement Control Order Entire Country 2020 (CMCO) starts  Movements were restricted by state borders  Interstate movement for stranded person were allowed on 7 May until 10 May only.

Table S2. Average concentration, variations before and during MCOs and relative change (%) of: PM2.5, CO, NO2, and SO2 for sub-urban stations.

-3 PM2.5 (µg m ) CO (ppm) NO2 (ppm) SO2 (ppm) Stations Region Before Before Before Before MCOs % MCOs % MCOs % MCOs % MCO MCO MCO MCO

Kangar N 12.96 10.5 -18.94+ 0.4707 0.4360 -7.36+ 0.0027 0.0015 -44.65+ 0.0005 0.0008 56.64+

Langkawi N 12.97 9.81 -24.34+ 0.4319 0.2759 -36.13+ 0.0042 0.0019 -55.38+ 0.0008 0.0011 30.09+

Alor Setar N 20.16 11.3 -43.93+ 0.5128 0.4962 -3.23 0.0049 0.0032 -35.43+ 0.0007 0.0005 -24.26+

Sg Petani N 19.01 11.84 -37.71+ 0.4425 0.3270 -26.10+ 0.0072 0.0044 -38.94+ 0.0007 0.0007 10.56+

Seberang Perai N 21.24 12.37 -41.76+ 0.7077 0.5120 -27.66+ 0.0072 0.0046 -36.72+ 0.0007 0.0007 0.33

Balik Pulau N 19.45 13.88 -28.65+ 0.5633 0.4263 -24.33+ 0.0039 0.0027 -30.25+ 0.0006 0.0008 29.64

Taiping N 25.25 11.75 -53.47+ 0.2407 0.1997 -17.04 0.0087 0.0041 -52.38+ 0.0011 0.0010 -2.66

Pegoh Ipoh N 18.87 15.09 -20.03+ 0.4181 0.3335 -20.24+ 0.0067 0.0037 -44.04+ 0.0003 0.0008 172.48+

Tg Malim N 9.52 7.36 -22.73+ 0.5198 0.4303 -17.22+ 0.0055 0.0026 -53.43+ 0.0005 0.0007 39.61

Batu Muda KL C 21.47 17.81 -17.02 1.1525 0.8349 -27.55+ 0.0161 0.0053 -67.16+ 0.0007 0.0005 -33.67+

Putrajaya C 21.96 16.23 -26.12+ 0.7058 0.4818 -31.74+ 0.0077 0.0037 -52.36+ 0.0011 0.0011 -0.61

Petaling Jaya C 25.49 16.45 -35.47+ 1.2540 0.5839 -53.43+ 0.0258 0.0082 -68.26+ 0.0009 0.0007 -23.80+

Klang C 25.57 22.17 -13.28 0.9501 0.6162 -35.14+ 0.0183 0.0087 -52.60+ 0.0010 0.0009 -10.42

Banting C 20.47 15.49 -24.34+ 0.7939 0.5151 -35.12+ 0.0101 0.0058 -42.52+ 0.0014 0.0012 -15.29+

Nilai S 23.53 15.78 -32.93+ 0.5377 0.3942 -26.68+ 0.0133 0.0067 -49.44+ 0.0011 0.0009 -20.62+

Port Dickson S 16.56 12.36 -25.37+ 0.5878 0.5170 -12.05+ 0.0073 0.0039 -46.90+ 0.0022 0.0011 -51.83+

Bukit Rambai S 15.8 12.39 -21.56+ 0.5253 0.4301 -18.12+ 0.0061 0.0036 -41.76+ 0.0012 0.0013 9.64

Segamat S 14.47 15.84 9.46 0.5606 0.5231 -6.69 0.0030 0.0029 -4.04+ 0.0011 0.0013 18.63

Batu Pahat S 12.87 10.13 -21.31+ 0.6688 0.5025 -24.87 0.0051 0.0028 -45.43+ 0.0019 0.0019 3.50

KotaTinggi S 8.08 7.2 -10.90+ 0.3905 0.4596 17.69 0.0017 0.0018 6.87+ 0.0008 0.0010 38.36

Tangkak S 14.81 11.3 -23.70+ 0.7606 0.5423 -28.71+ 0.0055 0.0027 -51.58+ 0.0009 0.0009 0.17

Temerloh E 14.61 12.38 -15.23+ 0.4509 0.3741 -17.02+ 0.0042 0.0020 -51.62+ 0.0009 0.0006 -33.46+

Jerantut E 15.52 10.25 -33.94+ 0.3113 0.3585 15.17+ 0.0026 0.0014 -47.56+ 0.0007 0.0005 -34.03+

Indera E 9.25 8.35 -9.68+ 0.3745 0.3810 1.72+ 0.0046 0.0019 -58.09+ 0.0012 0.0007 -39.57 Mahkota

Besut E 12.84 11.83 -7.89 0.6305 0.4821 -23.53+ 0.0018 0.0014 -23.30 0.0010 0.0007 -26.42+

Tanah Merah E 22.82 18.74 -17.87+ 0.6739 0.5478 -18.72 0.0052 0.0029 -44.85+ 0.0010 0.0008 -22.04+

Kota Bharu E 14.84 15.2 2.4 0.4208 0.4001 -4.91 0.0032 0.0023 -28.04+ 0.0012 0.0008 -29.27+

Tawau Sb 7.06 6.76 -4.23 0.5314 0.5864 10.34+ 0.0042 0.0027 -36.46+ 0.0005 0.0004 -15.49+ Sandakan Sb 11 9.09 -17.31+ 0.6142 0.5039 -17.96 0.0035 0.0016 -53.85+ 0.0007 0.0008 16.04+

Kota Kinabalu Sb 11.76 9.35 -20.51 0.5122 0.5564 8.64+ 0.0031 0.0012 -62.21+ 0.0016 0.0007 -52.73+

Labuan L 12.08 13.59 12.47 0.9920 0.6185 -37.65+ 0.0022 0.0014 -35.78+ 0.0008 0.0011 24.28+

Miri Sr 15.26 13.37 -12.43 0.5398 0.5366 -0.59 0.0040 0.0019 -51.22+ 0.0005 0.0005 1.00

Bintulu Sr 13.48 12.56 -6.8 0.4515 0.4457 -1.29 0.0042 0.0030 -29.41+ 0.0005 0.0003 -44.25

Sibu Sr 10.42 8.86 -14.98+ 0.2704 0.2435 -9.96 0.0041 0.0021 -49.35+ 0.0008 0.0009 17.34+

+ indicate average concentration before MCO vs average concentration during MCOs significant at p<0.05; NA: not available.

Table S3. Average concentration, variations before and during MCOs and relative change (%)

of: PM2.5, CO, NO2, and SO2 for urban stations.

-3 PM2.5 (µg m ) CO (ppm) NO2 (ppm) SO2 (ppm)

Stations Region Before Before Before Before MCOs % MCOs % MCOs % MCOs % MCO MCO MCO MCO

Seberang Jaya N 23.94 14.24 -40.51+ 0.8144 0.5786 -28.95+ 0.0131 0.0070 -46.46+ 0.0011 0.0009 -13.63+

Minden N 21.48 11.51 -46.43+ 0.6121 0.4764 -22.17+ 0.0085 0.0043 -49.79+ 0.0010 0.0009 -4.24

TasekIpoh N 19.73 14.24 -27.83+ 0.6512 0.4859 -25.37+ 0.0090 0.0035 -60.62+ 0.0009 0.0008 -2.99

Cheras C 21.35 14.5 -32.06+ 0.8069 0.5606 -30.53+ 0.0148 0.0051 -65.56+ 0.0004 0.0006 38.49+

Shah Alam C 19.77 16.12 -18.45+ 0.8392 0.6217 -25.92 0.0130 0.0065 -49.52+ 0.0012 0.0010 -13.12

Seremban S 13.96 11.61 -16.82+ 0.6157 0.4864 -20.99+ 0.0068 0.0027 -61.10+ 0.0008 0.0010 25.19

Bandaraya S -11.74+ 0.5487 0.5167 -5.83 0.0058 0.0033 -43.19+ 0.0008 0.0009 10.09 Melaka 14.25 12.58

Larkin S 14.3 13.4 -6.34 0.4559 0.3134 -31.25+ 0.0083 0.0041 -50.92+ 0.0018 0.0019 8.45+

Pasir Gudang S 10.6 10.76 1.5 0.5050 0.4718 -6.56+ 0.0047 0.0046 -1.66+ 0.0010 0.0011 13.22

Kuala E -4.93 0.5581 0.4595 -17.66 0.0040 0.0022 -43.63+ 0.0012 0.0009 -22.43+ Terengganu 15.7 14.92

Kuching Sr 9.13 8.43 -7.6 0.5564 0.5946 +6.86 0.0039 0.0024 -39.71+ 0.0002 0.0003 +61.15

+ indicate average concentration before MCO vs average concentration during MCOs significant at p<0.05; NA: not available.

Table S4. Average concentration, variations before and during MCOs and relative change (%) of: PM2.5, CO, NO2, and SO2 for industrial stations.

-3 PM2.5 (µg m ) CO (ppm) NO2 (ppm) SO2 (ppm)

Stations Region Before Before Before Before MCOs % MCOs % MCOs % MCOs % MCO MCO MCO MCO

Kulim N 20.18 11.21 -44.46+ NA NA NA 0.0084 0.0047 -44.33+ 0.0010 0.0011 10.23

Pengerang S 8.44 10.4 23.1800 NA NA NA 0.0027 0.0029 6.28 0.0013 0.0015 19.91+

Balok Baru E 12.05 9.15 -24.07+ NA NA NA 0.0058 0.0028 -51.85+ 0.0019 0.0006 -65.97

Kemaman E 16.47 11.27 -31.54+ NA NA NA 0.0023 0.0018 -19.02+ 0.0007 0.0008 21.64

Paka E 10.4 7.83 -24.72+ NA NA NA 0.0014 0.0009 34.61 0.0007 0.0007 -2.92+

Kimanis Sb 10.45 10.65 1.9900 NA NA NA 0.0020 0.0011 -46.38+ 0.0008 0.0007 -5.24+

Samalaju Sr 10.84 9.81 -9.5200 NA NA NA 0.0019 0.0016 -13.90 0.0010 0.0005 48.18

+ indicate average concentration before MCO vs average concentration during MCOs significant at p<0.05; NA: not available.

Table S5. Average concentration, variations before and during MCOs and relative change (%) of: PM2.5, CO, NO2, and SO2 for rural stations.

-3 PM2.5 (µg m ) CO (ppm) NO2 (ppm) SO2 (ppm)

Stations Region Before Before Before Before MCOs % MCOs % MCOs % MCOs % MCO MCO MCO MCO

Seri Manjung N 18.35 14.16 -22.85+ NA NA NA NA NA NA NA NA NA

Kuala Selangor C 15.54 14.27 -8.16+ NA NA NA NA NA NA NA NA NA

Alor Gajah S 11.52 10.71 -6.99 NA NA NA NA NA NA NA NA NA

Kluang S 9.22 8.03 -12.81 NA NA NA NA NA NA NA NA NA

Rompin E 9.12 12.1 32.74 NA NA NA NA NA NA NA NA NA

Limbang Sr 8.6 7.16 -16.69+ NA NA NA NA NA NA NA NA NA

Miri Sr 12.53 9.76 -22.14+ NA NA NA NA NA NA NA NA NA

Mukah Sr 6.78 6.42 -5.34 NA NA NA NA NA NA NA NA NA

Kapit Sr 6.38 6.34 -0.54 NA NA NA NA NA NA NA NA NA

Sarikei Sr 8.3 5.82 -29.91+ NA NA NA NA NA NA NA NA NA

Seri Aman Sr 7.32 6.56 -10.39 NA NA NA NA NA NA NA NA NA

Samarahan Sr 6.43 6.91 7.4 NA NA NA NA NA NA NA NA NA

+ indicate average concentration before MCO vs average concentration during MCOs significant at p<0.05; NA: not available.

Figure Captions

Fig. S1. Temporal variations of meteorological parameters during study periods.

Fig. S1.